Brick by Brick: Lego’s New Building Blocks describes Lego’s new Lego Factory initiative:
Customers create any structure they can imagine using Lego’s freely downloadable Digital Designer software. If they then decide to actually build their creation, the software, which keeps track of which pieces are required, sends the order to this corner of the Enfield warehouse. There, employees put all the pieces (which are grouped in standardized bags) into a box, along with instructions, and ship it off.